The present invention relates generally to improvements in writing instruments and it relates particularly to an improved multiple element writing instrument in which the writing elements may be selectively advanced to a writing position.
Protract retract dual writing element pens of the twist type are well known and widely employed. Such pens conventionally include a pair of manually accessible control components, one being a cylindrical cam and the other a longitudinal guide member and writing element engaging chucks which are restricted to longitudinal movement by the guide member having followers engaging the cam to effect such longitudinal movement of the chucks and writing elements with the relative rotation or twisting of the control components which alternatively effects the advance of a selected one of the writing elements and the withdrawal of the other.
The aforesaid twist type dual writing element is highly convenient to use but is generally complicated and expensive, requiring a large number of separate parts many of which are costly and a time consuming and laborious assembly calling for highly skilled labor. The conventional and known twist type dual element retractable pen is by reason of its complexity and cost unsuitable for use as a disposable or throw-away article.